In order to explore the characteristics and spatial distribution of soil Se content in Qingzhen, clarify its background and baseline values, and investigate the influences of soil parent rock, hypergene environment (soil pH, organic matter, soil type, etc.) and human activities (fertilization, irrigation, etc.) on soil Se content, in this study, 4 637 surface (0-20 cm) soil samples and 216 deep (150-200 cm) soil samples in Qingzhen were collected, and soil pH, organic matter, Se content and other indicators were determined. The results showed that the spatial distribution of Se content in surface and deep soils in Qingzhen were consistent, and the areas with high Se content were concentrated in the areas bordering Liuchang Township, Liwo Township and Zhanjie Township. The area of selenium-rich soil (0.4-3.0 mg/kg) in Qingzhen was 103 789.65 hm², accounting for 89.98% of the total area surveyed, and the background value of soil Se in Qingzhen was 0.56 mg/kg, and the baseline value of soil Se was 0.35 mg/kg. The background value of soil Se in Qingzhen was 1.93 times higher than the background value of soil Se in China, and higher than the background value of soil Se in Guizhou Province. The change rates of soil Se background (△RC_Se) were increased in different land use patterns and yellow soil, yellow-brown soil, lime soil and paddy soil in Qingzhen. Soil pH in Qingzhen was decreased by 0.15 unit from 2009 to 2019, and Se content of surface soil in Qingzhen was negatively correlated with pH and positively correlated with organic matter and deep soil Se content, and Se element was more likely to be accumulated and enriched in the environmental conditions of soils with strong acidity and rich organic matter. Se content was the highest in soils derived from basalt and the lowest in soils derived from purple sand shale. Both irrigation water and fertilizers in Qingzhen could bring Se into the soil, and the amount of Se brought in by irrigation water was large, with an average annual amount of 2 205 mg/hm².